a) Try writing the compounds mentioned in the chemical reactions in their formula form , and place them in the equation left or right as mentioned.
For example : A reacts with B to form C and D
Equation : A + B = C + D
b) Energy is required to break the bonds and released when the bonds are formed. The net sum of these energies , form the basis of enthalpy of the reaction.
For ex, AB + C = AC + D
Suppose A-B bond energy is 100 KJ/mol
and A-C bond energy is 150 KJ/mol
So enthalpy = 150 - 100 = +50 KJ
c) Always look for the sign of enthalpy to detemine whether the reaction is exothermic or endothermic.
If the sign is positive , the reaction is endothermic , if the sign is negative , the reaction is exothermic.
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